function request(url, callback) {
  let httpRequest;
  httpRequest = window.XMLHttpRequest ?
    new XMLHttpRequest() : window.ActiveXObject ? new ActiveXObject() : undefined;

  httpRequest.open('GET', url);
  httpRequest.send();

  httpRequest.onreadystatechange = function () {
    if (httpRequest.readyState === 4 && httpRequest.status === 200) {

      // callback(httpRequest.responseText);

      $observer.emit('get.lengthList.success', httpRequest.responseText);
    }
  };

  httpRequest.onerror = function () {
    $observer.emit('get.lengthList.fail', httpRequest.errorText);

  }
}
